Seismic surveying is a method for determining the structure of subterranean formations in the earth. Seismic surveying can utilize seismic energy sources that generate seismic waves, and seismic receivers that are positioned to detect the seismic waves. The seismic waves propagate into the formations in the earth, where a portion of the waves reflects from interfaces between subterranean formations. The reflected seismic waves are detected by the seismic receivers, which convert the reflected waves into representative data. The data can be transmitted by electrical, optical, radio or other techniques to devices which record the data. Through analysis of the recorded data, the shape, position and composition of subterranean formations can be determined.
Land seismic surveying is a method for determining the structure of subterranean formations beneath the surface of the earth. Seismic sources and seismic receivers for land seismic surveying can be placed on the surface of the earth. In different examples, the seismic source(s) or seismic receiver(s), or both, may be placed in a borehole for vertical seismic profiling.
Marine seismic surveying is a method for determining the structure of subterranean formations underlying bodies of water. Marine seismic surveying can utilize seismic energy sources and seismic receivers located in the water and can be towed behind a vessel or positioned on the water bottom from a vessel. Marine seismic surveying can also employ seismic receivers deployed on a seabed cable (which is provided on a seabed).
In marine seismic surveying, seismic waves do not reflect just from the interfaces between subterranean formations. Seismic waves also reflect from the water bottom (e.g., seafloor) and the water surface (e.g., sea surface), and the resulting reflected waves themselves continue to reflect. Waves that reflect multiple times are called “multiples.” Waves that reflect multiple times in the water layer between the water surface above and the water bottom below are called “water bottom multiples” or “water layer multiples.” The presence of water layer multiples in recorded seismic data can reduce the accuracy of seismic processing and interpretation techniques.